Fix for Drupal calling out missing features; APCu and Output Buffering following a clean installation.

[kelvtech-co-uk]

Hi, this is my first PR to a proper repo and not just my own so please forgive any bad practices.

I noted after clean install Drupal's 'Status Report' was showing some missing features. After a little digging I found that the

• Upload Progress complaint should be ignored as per the TL;DR note here.
• That Output buffering is discussed here and is now recommended.
• And that APCu is discussed here and to my read suggests its a benefit out of the box.

[m-rtijn]

From what I gather, the 'correct' approach seems to be to create a custom image with a Containerfile (or Dockerfile if you like) like this:

FROM docker.io/library/drupal:<your version here>

RUN mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"

# Possibly alter the default production ini as provided by the php role here

See the documentation of the upstream php image: https://hub.docker.com/_/php/, and see this discussion here: #256 (comment)